Thrombosis, the formation of a clot or thrombus in the cardiovascular system from the constituents of blood, is a potentially life threatening condition. Thrombosis can develop in any part of the cardiovascular system, but is most common in veins, particularly the deep veins in the leg. Thrombosis can result from a variety of causes including poor circulation, trauma, prolonged bed rest, or hip surgery, for example. In the arteries, thrombosis can be caused by arteriosclerosis. Thrombosis can develop in cerebral vessels, as well.
If a portion of the thrombus separates and is transported through the cardiovascular system, it can cause an embolism, or blockage of a blood vessel. A thrombus in a deep vein in the leg can cause a pulmonary embolism. A thrombus in a coronary artery can cause myocardial infarction. Similarly, a thrombus in a cerebral artery can cause cerebral infarction.
During the early development of thrombosis, up to about seven days, the thrombus is soft and can be treated by a variety of techniques. Application of urokinase to a clot under pressure has shown improved results over diffusion. Blinc, A., et al., "Dependance of Blood Clot Lysis on the Mode of Transport of Urokinase into the Clot--A Magnetic Resonance Imaging Study In Vitro," Thrombosis and Haemostosis, 65(5) 549-552 (1991). A pulse spray of urokinase has been directed onto soft thrombi to mechanically break up and dissolve it. High pressure water has also been directed onto the thrombus to destroy it. The thrombus can also be broken by a laser or a drill. The broken or dislodged portions of the thrombus are aspirated through a catheter so that they cannot migrate and obstruct other vessels of the cardiovascular system. Results have been mixed, with some treatments damaging tissue, causing another thrombotic or stenotic process. A surgical procedure may be required to remove the thrombus, as well.
Drug delivery in the cardiovascular system is also used to prevent restenosis percutaneous transluminal coronary angioplasty (PTCA) and percutaneous transluminal angioplasty (PTA). Drugs and other agents are delivered to lumens, vessels and cavities in other portions of the body, such as the urethra, bladder, prostate, rectum, bile duct, pancreatic duct and central nervous system, such as along the spinal column, to treat a variety of conditions, as well.